Study On The Intensification Mechanism Of Conditioning Process Based On Turbulent Field Characteristics

With the increasingly poor,miscellaneous and finer of mineral resources,flotation as an effective method for the separation of fine minerals that difficult to select,has been widely used in the utilization of mineral resources.As the pretreatment technology of mineral flotation,conditioning process play an important role in strengthening dispersion of particles and reagents,promoting the interaction between particles and agents,and improving the surface characteristics of particles.In recent years,the research on the floating-conditioning process mainly focuses on the study of the flow field characteristics and the structural optimization design of the conditioning device,while few researches have been carried out from the perspective of microscopic characteristic parameters of flow field.In this paper,the microscopic characteristic parameters of turbulent field were taken as the starting point,the energy dissipation scale distribution of turbulent field in the stirred tank and the strengthening mechanism of conditioning process were deeply studied,so as to further enrich the basic research of conditioning process that based on the flow field strengthening,and provides theoretical guidance for the process strengthening design of pulp conditioning,which has great theoretical value and engineering significance.The spatial distribution characteristics of the turbulent vortex dissipation microscale of fluid in the stirred tank under different turbulent field patterns were analyzed through the numerical calculation of single phase flow,and the results showed that the turbulent vortex dissipation microscale in the tank could be reduced by increasing the rotation speed,as well the turbulent vortex dissipation microscale increases gradually with the increase of r/R.The turbulent field pattern in the tank determined the evolution behavior of turbulent vortex dissipation microscale in axial height and radial position,and the minimum value of the turbulent vortex dissipation microscale in the tank was 8.58μm when r/R=1.07.The distribution law of turbulent vortex dissipation microscale in the characteristic area of stirred tank which action by different patterns of turbulent flow field were further analyzed,and the polynomial mathematical models in the characteristic area under axial turbulent field and radial turbulent field were built which showed the distribution of turbulent vortex dissipation microscale along the radial position at different heights.Based on the numerical calculation of euler two-phase flow,the volume distribution characteristics of particle with different particle sizes under the action of turbulence were clarified.The increasing regularity of the suspension uniformity that strengthened by the turbulent field of fine grain were defined,that was,the axial turbulent field<the radial turbulent field<the compound turbulent field.The influence of solid phase particle on the turbulent vortex dissipation microscale in the stirred tank which associated with the turbulent field pattern were analyzed,and the results show that the influence range of solid phase particles on the turbulent vortex dissipation microscale at axial height decreases as the increase of impeller rotational speed under the axial turbulent field,while the solid particles in the radial and compound turbulent field significantly increased the turbulent vortex dissipation microscale of fluid outside the impeller region.The pulp concentration distribution in the stirred tank was tested by experiments,and the pulp concentration prediction models of 2×8×1,2×6×1 and2×8×1 under axial,radial and compound turbulent fields were determined by neural network.Taking the size distribution rule of particle agglomeration that conditioning by turbulent field enhanced as the cutting point,three evolution stages of particle agglomeration in radial and compound turbulent field were determined:the formation of agglomeration,the rupture of agglomeration and the agglomeration generated again.The mineralization behavior in conditioning system with different patterns of turbulent field was investigated,that was the mineralization degree of pulp was highest in the compound turbulent field.On the basis of atomic force microscopy,the influence of turbulent field pattern on the separation distance and adhesion force between quartz particles were analyzed,which indirect revealed the effect of turbulent field pattern on the adsorption property between quartz particles and reagent.The corresponding relationship between the turbulent vorticity and the turbulent energy dissipation rate was determined based on the stirred tank system under the action of turbulent field.Based on the force analysis at axial direction of particle in the stirred tank,the governing equation of the homogenization distribution in the micro-element control area was established.The relationship between the suspension dispersion properties of solid particles and the turbulent vortex dissipation microscale and turbulence intensity in stirred tank was investigated,in other words,the effect of turbulent dissipation microscale on the off-bottom suspension of particles with different sizes was different,and high turbulence intensity was a necessary and insufficient condition for the uniform distribution of solid particles in the tank.The agglomeration probability equation between particles in the turbulent flow field was derived by taken the particle followability,particles collision probability,particles agglomeration behavior and agglomeration fracture mechanism as research points.Fly ash was selected as the test sample to study the mixing conditioning macroscopic effect of fly ash under the action of different patterns of turbulent field.By the studied of fly ash conditioning-flotation experiments,the results showed that the cumulative unburned carbon recovery of fly ash conditioning by axial turbulent field was much smaller than the radial and compound turbulent field,and the maximum flotation rate constant value of 0.0862 s^-1,the minimum loss on ignition of tailing ash of 2.33%were obtained by the conditioning of compound turbulent field at the conditioning speed of 1500 rpm,which the effect of turbulent field pattern on flotation kinetics and decarbonization performance of fly ash was verified.The significance analysis showed that the mixing conditioning velocity under the compound turbulent field significantly affected the carbon removal rate and loss on ignition in fly ash flotation.It is proposed that the region equilibrium configuration of turbulent intensity and turbulent vortex dissipation was the direction to realize the process intensification of mixing conditioning.Based on the above research,it is proposed that the equilibrium configuration of the turbulence intensity and the turbulence vortex dissipation area in the pulp conditioning system is the key to realize the process intensification of conditioning.The paper has 180 figures,38 tables,and 185 references.